so i recently replaced the driver and output transistors on the 730 because i shorted them out a while back. anyway, the amp is working again.

there is another problem. when i power on the amp with either speakers or headphones connected there is a hissing noise for a couple seconds in the left channel then it ceases. there is then a hissing noise in the right channel then it ceases.

any ideas what could be causing this?

edit:

the hissing noise is a large temporary DC offset ~100mV reaching the speakers. any ideas what could cause that?

It could be normal. Mine also makes some strange noises as everything begins powering up. Takes about 3 seconds. If you look at the operators manual, you will see that they recommend disengaging the speakers prior to turning the unit on and then engaging them after a few seconds. I usually just disconnect them (via the speaker selector) every time I turn the unit off. My offset goes off the scale on turn on with the speakers engaged.